A standard glass-grinding or -polishing apparatus has a cylindrical drum whose surface is covered with grit typically in the form of carbide, carborundum, or diamond particles. This drum is rotated about its axis while it is urged radially against the surface to be ground or polished.
Such a device is relatively efficient at smoothing the perpendicular edge of a piece of glass but cannot be used to bevel an edge. To do so requires orienting the axis of the drum at an angle to the support on which the sheet is lying, and then accurately moving the drum. Such operation is impossible to effect with smooth results.